I begin this thesis by reviewing the use of the concept of tradition in the disciplines of theology and literary criticism. In Chapter II I discuss a number of concepts for which ‘tradition’ is often used as a synonym. Then, by considering traditions in the arts and sciences, I attempt to produce a model of 'tradition' for which there is no synonym. In that model, innovation is identified as being indispensable, rather than antithetical, to a tradition’s vitality. In Chapter III I consider some influential notions of what constitutes a tradition in the history of political thought. In objecting to the idea that traditions are prescriptive, or paradigmatic, I suggest that political ideologies are traditions of discourse, and, therefore, that it is a mistake to contend that any given ideology can be identified by a simple definition. Location of that identity requires, in my view, an historical narrative of innovation in a tradition of discourse. Such a narrative, I argue in Chapter IV, should not be merely an account of the philosophies, alleged to have influenced political agents, with, perhaps, an account of those agents' policies. It should include a discussion of the vocabulary of ideological debate. In particular, I suggest that the actions of the ideologically committed are symbolic affirmations of their ideological identity, and, therefore, that the intelligibility of accounts of party authority and orthodoxy is enhanced by an appreciation of the vocabulary of ideological committment. Finally, I propose an objection to Skinner's view that professed principles can be treated as 'causal' conditions of an agent's actions. My conclusion is that the historian of political ideas should narrate the history of a tradition by recounting the political experiences of an association of political agents in the light of the changing vocabulary in which that experience has been articulated.